The present invention relates to a vacuum isolating valve for an electron-bombardment welding machine, of the type having a welding enclosure to receive work parts to be welded, a gun which emits a beam of electrons and focuses it on the parts, and means for creating a vacuum in both the enclosure and the gun, the valve being adapted to occupy an open, welding position in which it opens communication between the enclosure and the gun and allows electrons to pass, and a closed, non-welding position in which it breaks such communication and allows the work parts to be inspected and, if necessary, inserted, withdrawn or adjusted in the enclosure.
In machines of this kind which are known at present, the welding enclosure and the volume of space within the gun, that is, the gun housing which contains the cathode, the surrounding cylinder and the anode, generally are divided into two separate spaces between which a transverse dividing partition is provided, the central part of this partition being provided with an orifice for the electrons emitted by the cathode to pass through. While the electrons are passing, i.e., during welding, a high vacuum needs to prevail in these two spaces, the vacuum being of the order of 10.sup.-5 mm of mercury for the gun housing and 10.sup.-2 mm of mercury for the enclosure; any higher pressure would soon lead to the electrons scattering. The vacuum is generated and maintained by suitable pumping means such as two separate pumps which are assigned in the one case to the welding enclosure and in the other to the gun. To enable the enclosure to be opened (and thus the pressure in it to be raised to atmospheric) whenever it is necessary to gain access to it in order to introduce or withdraw parts, but at the same time so that this can be done without affecting the vacuum within the gun, the orifice through which pass the electrons is fitted with a vacuum-tight valve which enables the orifice to be blocked and the gun to be thus isolated from the enclosure.
Such welding machines may also be equipped with an optical arrangement for insepcting the parts to be welded, which may be formed by a light source, a viewing device such as a magnifier, and a system of mirrors or the like which reflect light from the source onto the parts to be welded along the axis of the electron beam, and then return the light which is reflected by these parts to the viewing device, which enables the electron beam to be accurately lined up with the joint line between the parts before the welding operation and also enables the quality or standard of the welds to be checked visually.
Certain of the valves in current use are ones which contain a rotary valve body provided with a passage. In the case of machines fitted with an optical inspection arrangement, the said mirrors are mounted on the rotary valva body. Depending on the angular position of the valve body, the valve is either in the open, or welding, position, when the passage is lined up with the electron beam orifice to allow the electrons to pass while providing communication between the gun and enclosure, or in the closed position, when the electron beam orifice is blocked (the electron beam having previously been cut off) while the mirror system lies on the optical path of the optical inspection system, thus enabling the parts to be viewed. The rotary valve body must occupy a precise angular position if it is to provide a perfect seal and an accurate line of sight. If there is any divergence from this position, as a result of friction for example, there is a danger of leaks arising and the line of sight being incorrect.
Also known are so-called slide valves which are formed in essence by a core or slider which is slidably moved by a linkage system. Such valves have serious disadvantages one of which is that the linkage mechanism is complicated and costly to construct, is easily upset and is not very easy to operate. The mechanism is also subject to jamming and play.
It is an object of the invention to provide a valve which is of simple and economical construction and is reliable in operation.